DW and took the cruise quite a while ago. Our itinerary started in Lyon, a city that many consider the gustatory capital of France. If I were to take it again I would spend a couple days in Lyon.
We sailed up the Saone to Beaune, a great Burgundy wine town with a medieval look. We had tastings at a couple cellars and had an opportunity to ship some wine home (we didn't). It was raining the day we were there, so we didn't get to explore much on foot. After Beaune we backtracked to the confluence with the Rhone at Lyon, with a brief stop at Macon (known for white wine) on the way.
On the Rhone, we toured Vienne, site of numerous Roman ruins, including a theater and a well-preserved temple. There's also a Romanesque Christian church. We overnighted in Tournon/l'Hermitage.
The next day I suspect we stopped in Valence, although I can't recall -- it looks like a city of note with some historical significance, and the river flows through the center of town. A nice feature of this cruise is that you disembark in the center of each port of call, which is especially nice in cities like Avignon and Arles.
We overnighted in Viviers, a medieval French village. One of our on-board guides had a home there and took us there for a tour.
The next day we visited the Roman aqueduct at Pont du Gard, which required a short bus ride. Then we arrived at Avignon and its papal palace. The next day was Arles, where, IIRC, the actual cruise ended. Our tour included a couple days at Aix-en-Provence (lovely, lively city) along with a day trip to Marseille, where we began our return flight home.
Before we did that, though, we rented a car and explored the Camargue and other parts of Provence for a few days. I highly recommend a side trip through the Camargue if you can swing it.